(a) Field of the Invention
The present invention relates to a liquid crystal display (LCD) and, more particularly, to an LCD in which a predetermined opening pattern is formed at pixel and common electrodes such that a wide viewing angle is obtained.
(b) Description of the Related Art
Generally, an LCD has a structure having a liquid crystal layer that is sandwiched between two substrates. An electric field is applied to the liquid crystal layer to control the alignment of the liquid crystal molecules, ultimately controlling the transmittance of incident light. In a vertically alligned (VA) LCD, the liquid crystal molecules are aligned perpendicular to the substrates when an electric field is not applied. In case two polarizer films are arranged with their polarizing directions perpendicular to each other, the linearly polarized light passing through the first polarizer film is completely blocked by the second polarizer film in the absence of an electric field. The complete blockage of lights exhibits a very low brightness in an “off” state of the normally black mode. This helps a VA LCD obtain a relatively higher contrast ratio than that of the conventional TN liquid crystal display.
However, the liquid crystal molecules are irregularly inclined against the substrate when an electric field is applied. Therefore, in one or more areas, the long axis directions of some of the liquid crystal molecules are aligned with the polarizing direction of the first polarizer film or the second polarizer film. In such areas, the liquid crystal molecules cannot rotate the polarizing direction, i.e., polarization, and the light is completely blocked by the polarizer film. Such areas appear as black portions on the screen, which degrade the in picture quality. These areas are referred to as areas of “texture.”
In order to solve the above problem, several techniques of electrode-patterning have been suggested. However, a slow response time still remains as a problem.
FIG. 1 illustrates a schematic view of opening patterns formed at pixel and common electrodes in a prior art liquid crystal display. As shown in FIG. 1, the pixel and common electrodes are formed with opening patterns 1 and 2, respectively. Each of the opening patterns 1 and 2 is formed in a V-shape and is arranged with ends of the V-shapes in proximity to each other so that roughly a diamond shape is formed by the opening patterns 1 and 2. Liquid crystal material is injected between the pixel electrode and the common electrode, and liquid crystal molecules 3 are aligned perpendicular to the electrodes.
When an electric field is applied to the liquid crystal material, the liquid crystal molecules 3 come to be arranged parallel to the electrodes. However, the response speed of the liquid crystal molecules 3 with respect to the applied electric field is very slow with the formation of the opening patterns 1 and 2 at the pixel and common electrodes. That is, as a result of a fringe field formed due to the opening patterns 1 and 2, the liquid crystal molecules 3 are first arranged perpendicular to the opening patterns 1 and 2 (A state), then are aligned to be parallel with one another (B state), because liquid crystal molecules tend to align themselves roughly parallel along their long axes. These two steps of alignment slow down the response speed.
The slow response speed of liquid crystal molecules generates after-images when displaying moving pictures on the screen. There is therefore a need to increase the response speed of liquid crystal molecules.